A DC-to-DC converter is a device that accepts a DC input voltage and produces a DC output voltage. Typically the output produced is at a different voltage level than the input. In addition, DC-to-DC converters are used to provide noise isolation, power bus regulation, etc. Many popular DC-to-DC topologies are based upon flyback converters, which incorporate an inductor to provide voltage boost and usually implemented in boost or buck/boost topologies.
Although flyback converters can be controlled in a linear fashion through a broad range, this range does not include the regime approaching zero output. As switching delays of the switching element used become significant in relation to the commanded pulse width, severe deviations from linear operation occur. Linear operation of flyback converters is, however, sometimes desired inclusive of zero output. A need exists to thus extend the operating range.